Photoprinting apparatus



March 1 1, 1969 J. c. A. VERCOULEN 3,432,236

PHOTOPRINTING APPARATUS Filed July 21, 1966 INVENTOR Jaw/mm (mm/sAwwr/M/J Vmcoamv BY W.

- ATTORNEY United States Patent 3,432,236 PHOTOPRINTING APPARATUSJohannes Cornelis Augustinus Vercoulen, Blerick, Netherlands, assignorto 'Chemische Fabriek L. van der Grinten N.V., Venlo, Netherlands, acorporation of Dutch law Filed July 21, 1966, Ser. No. 566,801 Claimspriority, application Netherlands, July 23, 1965,

6509596 U.S. Cl. 355-109 Claims Int. Cl. G03b 27/12 ABSTRACT OF THEDISCLOSURE The invention relates to photoprinting by the use ofapparatus of the type which comprises a rotatably driven exposurecylinder which is provided With a clamping device for holding theleading edge of an original to be copied and a driven belt system forpressing the nonheld part of the original together with a sheet oflight-sensitive material against the wall of the cylinder duringexposure. Apparatuses of this type generally function in a satisfactorymanner when the original is copied once or only a few times. Usually theexposure cylinder is driven through contact With the belt system, ifnecessary via the original and the light-sensitive material situated inbetween, and thus with the same circumferential velocity as the beltsystem.

If in such an apparatus an original is rotated many times by theclamping device in order to make a larger number of copies, it is oftenfound that the original is not taken along properly by the clampingdevice and that it becomes detached from the clamping device, inconsequence of which the transport of the original naturally isseriously upset and the original is often damaged.

Naturally the detachment of the original can be obviated by increasingthe force with which the clamping device holds the original. Inpractice, however, it is dilficult to realize this; as a rule theconstruction of a clamping device capable of supplying the desiredforces occupies an impractically large space, with all the disadvantagesinvolved, while there is a great risk that the cylinder may be damagedby the forces set up.

It has been found that the nature of the original to be copied largelydetermines the occurrence of the difiiculties described. Folded orsomewhat wrinkled originals will become detached sooner from theclamping device than smooth, flat originals, whilst originals made ofthin material (writing paper and the like) are not detached as readilyas originals made of thicker material (photographic film and the like).

It is not quite clear to what factor the detachment of the original hasto be imputed. However, the striking fact has been observed that thephenomenon can be prevented by providing that the velocity with whichthe belt system is driven is somewhat higher than the velocity withwhich the cylinder is driven. Preferably the velocity of movement of thebelt system is 0.5-3% higher than the velocity of movement of thecylinder.

It is remarked that it is known to apply a much higher difference inspeed between a glass cylinder without a clamping device and a drivenbelt system in photoprinting apparatus, in which the sheets aretransported by friction between these parts, in order to smooth outdilferences in transparency and faults in the glass cylinder as appearsfrom British patent specification 631,916. In this known apparatus thesheets move with the belt system and slide over the smooth glasscylinder.

The invention will now be described further with reference to theaccompanying drawing, in which a photoprinting apparatus according tothe invention is schematically illustrated in cross-section.

In this figure, 1 is the glass exposure cylinder of the apparatus, whichis supported at its ends in a conventional manner in end plates so as tobe freely rotatable. A tubular copying lamp 2, as well as a screen 3,which prevents undesirable radiation of light towards the operating sideof the apparatus, are stationarily mounted inside the cylinder.

Stretched around the cylinder is a system of juxtaposed belts 4, whichare also guided over a driving roller 8 and over rollers 5, 6, 7, whichserve to guide and stretch the belts. At least one of these rollers,e.g., roller 7, is provided with disks 9, which extend between the belts4 and which serve to guide the belts and to form slit-shaped interspacesbetween the belts.

The parts 2 and 3 and the rollers 5 to 8 are also supported in the saidend plates in a usual manner.

A clamping device, known per se, which serves to hold the leading edgeof an original to be copied, is attached to the cylinder 1. Thisclamping device comprises a shaft 10, which is rotatatbly supported inbearings (not shown) which are carried by the cylinder and to which areattached a number of mutually spaced clamps 11 and ejecting pins 12,which extend through openings in the cylinder wall. The members 11 and12 respectively are at the same time situated in the region of theslit-shaped spaces between the belts 4, and they are dimensioned in sucha way that they are able to extend through these spaces.

In a conventional manner the clamping device is normally kept closedwith the aid of springs (not shown), which tend to press the clamps 11against the wall of the cylinder 1. With other conventional means, e.g.,by means of a cam and a plunger or by means of an electromagnet, theclamping device can be opened at the desired moments by turning theshaft 10 contrary to the action of the said springs.

The apparatus is further provided with a device, known per se, forfeeding originals, which consists of guide plates 13 and 14respectively, a rotatably supported shaft 15, to which stops 16 and acontinuously rotating transport roller 17 are connected. An original tobe copied O is placed between the plates 13 and 14 in such a way thatits leading edge rests against the stops. When the shaft 15 is turned,the stops 16 swing away, while at the same time the rotating transportroller 17 seizes the original and sets it in motion. The apparatus isnow controlled in such clamping device of cylinder 1, which at thatmoment, in the opened position, moves past the original-feedingmechanism, and that afterwards the clamping device is closed and theoriginal starts rotating along with the cylinder.

Furthermore the apparatus comprises a conventional device for feedingsheets of light-sensitive material, which device consists of guideplates 18 and 19 respectively, a rotatably supported shaft 20, stops 21,and a rotating transport roller 22. This device is controlled in thesame way as mentioned hereinbefore with regard to the original-feedingmechanism, so that with each revolution of cylinder 1 a light-sensitivecopy sheet K is put on the original 0 between cylinder 1 and belts 4,with a view to making a copy.

After the exposure the copy sheet is sucked against the belts 4 by meansof a suction 'box 23, so that it is detached from the cylinder and via aguiding plate 24 is guided away, e.g., to the developing unit of theapparatus.

When the desired number of copies of an original has thus been made, theclamping device is opened. The clamps 11 release the edge of theoriginal, while the ejecting pins 12 separate the edge of the originalfrom the cylinder wall and guide it over a guiding plate 25, along whichthe original is afterwards guided away, e.g., to a receiving trough.

All the parts such as guide plates, shafts 15 and and box 23 are mountedbetween the said end plates.

The belts 4 are driven by the driving roller 8, which is a way that theleading edge of the original gets into the coupled to the driving motor(not shown) of the apparatus. This motor is positioned at the outside ofthe apparatus, i.e., outside one of the end plates.

Outside one of the end plates, cylinder 1 is provided with a pulleyunit, over which a belt 26 is guided, which is tensioned over a tensionroller 27 and extends over a driving roller 28. Mounted on the roller 28is a gear wheel 29, which co-operates with a .gear wheel mounted on theroller 8, and via these gear wheels, the roller 28, and the belt 2-6,the cylinder 1 is also coupled to the driving motor of the apparatus.

The diameters of therollers 8 and 28 respectively and the number ofteeth of the gear wheels 29 and 30 respectively are so chosen that therequired difference between the velocities with which the cylinder 1 andthe belts 4 are driven is set up. The desired difference can of coursebe obtained in various ways. The driving rollers 8 and 28 respectivelymay have the same diameter and the gear wheels 29 and 30 respectivelymay have different numbers of teeth, the gear wheel 30 having slightlyfewer teeth than the gear wheel 29. For example, gear wheel 30 may havefifty-nine teeth and gear wheel 29 sixty. The two gear wheels may alsobe equally large and the diameter of roller 8 be somewhat larger thanthat of roller 28. Preferably the diameter of the roller 8 is 0.5-3%larger than that of the roller 28 if the gear wheels 29 and 30 have thesame number of teeth, and anyhow the diameters of rollers 8 and 28 andthe numbers of teeth of gear wheels 29 and 30 are chosen so that thelinear speed of the belt-s 4 is 0.5 to 3% higher than the peripheralspeed of glass cylinder 1.

A very convenient form of the apparatus is obtained when a conventionalrope pulley with a variable diameter is used for the roller 28. In suchan embodiment it is very easy to realize the desired difference invelocity.

It will be clear, that in the cross-section shown in the drawing thegear wheels 29 and 30 and the belt 26 will in reality not be visible asthey are positioned behind 4 i an end plate. For sake of simplicity,however, these parts are shown in full lines.

What I claim is:

1. Photoprinting apparatus comprising a rotatably driven exposurecylinder, which is provided with a clamping device for holding theleading edge of a sheet original to be copied and a driven belt systemfor pressing the nonheld part of the original together with sheetlightsensitive material against the wall of the cylinder duringexposure, and means for driving the belt system at a speed slightlyhigher than the speed of the cylinder.

2. Apparatus according to claim 1, wherein the said means provide thatthe velocity of movement of the belt system is 0.5-3% higher than thevelocity of movement of the cylinder.

3. Apparatus according to claim 1, said cylinder being driven by anonslipping belt drive comprising a driven rotary pulley, said drivingmeans comprising a rotary member engaging the belts of said belt systemand means coupling said member with said pulley for rotation therewithat a relative speed advancing said belts slightly faster than saidcylinder surface.

4. In a process of exposing photoprint materials by laying alight-sensitive sheet upon an original sheet having its leading edgegripped to a rotating exposure cylinder and carrying said sheetstogether on the surface of said cylinder through an exposure zone whilepressing them against said surface by a system of belts wrapped againstand moving in the same direction as said surface, the improvement whichcomprises driving said cylinder at a speed desired for exposure of saidsheets in said zone and driving said belts at a speed slightly higherthan the speed of movement of said surface, to avoid detachment of theoriginal sheet from the cylinder.

5. A process according to claim 4, the speed of said belts being 0.5 to3% higher than the speed of said surface.

References Cited UNITED STATES PATENTS 2,048,754 7/1936 Putnam 226-1712,297,573 9/1942 MacDonald et a1. 77.5 3,033,095 5/1962 Limberger95--77.5 3,199,864 8/1965 Irvine 27151 NORTON ANSHER, Primary Examiner.

CHARLES B. FUNK, Assistant Examiner.

US. Cl. X.R. 27l5l; 355-

